Fatty Liver (cont.)

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

What is the difference between nonalcoholic fatty liver and steatohepatitis?

As discussed previously, the difference between isolated, nonalcoholic fatty
liver and steatohepatitis (NASH) is the presence of inflammation and damage to
the liver cells in NASH; in both, the liver has increased amounts of fat.
Although about a third of the general population has fatty liver, approximately
10% have NASH. Approximately one third of patients with NAFLD have NASH. Although fatty liver and NASH appear to arise under the same conditions, it does not appear that fatty liver progresses to NASH. Thus, whether a patient is to develop fatty liver versus NASH is determined very early during the accumulation of fat, although it is unclear what factors determine this. It is believed that the inflammation and damage of liver cells are caused by the toxic effects of the fatty acids released by fat cells, but fatty acids in the blood are elevated in both fatty liver and NASH. Perhaps the difference is explained by genetic susceptibility as suggested by preliminary data.

The consequences of fat in the liver depend greatly on the presence or absence of inflammation and damage in the liver, i.e., whether there is fat alone or NASH is present. Isolated fatty liver does not progress to important liver disease. NASH, on the other hand, can progress through the formation of scar (fibrous tissue) to cirrhosis. The complications of cirrhosis, primarily gastrointestinal bleeding, liver failure, and liver cancer, then may occur.

What is the relationship between nonalcoholic fatty liver disease, obesity, and diabetes?

As discussed previously, obesity and diabetes have important roles in the development of fatty liver. Whereas
one third of the general population (which includes obese and people with
diabetes) may develop NAFLD, more than two thirds of people with diabetes
develop NAFLD. Among patients who are very obese and undergoing surgery for
their obesity, the majority have NAFLD. Moreover, whereas the risk of NASH is
less than 5% among lean persons, the risk is more than a third among the obese. Fatty liver increases both in prevalence as well as severity as the degree of obesity increases. The increases begin at weights that are considered overweight - i.e., less than obese.